Reproduction and Development 113
in an umbrella-shaped structure. In smaller, flexible sharks, the male may
wrap himself around the female’s body, whereas larger, stiffer sharks swim
side-by-side or belly to belly. Male Spotted Eagle Rays grab a pectoral fin,
rotate, and swim upside down under the female while inserting a clasper.
Actual copulation may last less than two minutes in Eagle Rays or up to
four hours in Clearnose Skates (Raja eglanteria).
Regardless of species, once a clasper is inserted, the male pumps sperm
into the female’s reproductive tract, the sperm propelled in part by sea wa-
ter pushed from a muscular bladder at the base of his claspers. Females
often bear bite marks and ragged scars on parts of their body from these
mating encounters, some the result of a female pulling herself away before
a male can insert a clasper.
Thanks to a multiyear study conducted by researchers in the Dry Tor-
tugas marine reserve in south Florida, the shark species whose mating be-
havior we know best is the Nurse Shark. Nurse Sharks are common around
southern Florida, live in shallow water, and can be observed while they are
mating if researchers approach them carefully. Sometimes several males
pursue a female simultaneously, until one grabs her by her pectoral fin and
attempts to carry her into deeper water where he has room to copulate. A
female may avoid the advances of a male by moving into shallower water
and even burying her pectoral fins in the sand, making it harder for a male
to grab her. When a male does succeed in grasping her fin, she may then
quickly roll over on her back above the male, trying to twist loose, and push
her ventral surface and cloaca in the air, waiting for him to give up. (Some
female rays avoid copulation by burying in the sand, slapping their pec-
toral fins on the surface, and sometimes stabbing a male with their barb.)
She may shake loose but in the process sustain damage to her pectoral fin
Few sharks have been observed
mating, and even fewer have been
filmed. This photo was taken just
as a male Nurse Shark grasped the
right pectoral fin of a female. The
female is to the right in the picture,
on her left side. Photo © Jeffrey C. Carrier,
all rights reserved; used with permission